Joxe 17, 1915] 

NATURE 

latter statement corresponds fully with our own 
experience. For the rest, the book treats in detail 
of the Thalamiflore, Calyciflore, and certain 
Gamopetale; descriptions of the plants and their 
natural orders are given, and there are numerous 
illustrations reproduced from photographs. 
The author states that “the facts of botany, 
like those of zoology . . . are capable of reduction 
to orderly arrangement,” and it is to be regretted 
that he has not found himself able to follow out 
his opening text in the ordering of his material. 
The third volume recently issued completes the 
work. There are 95 pages of introduction deal- 
ing with germination, plant formations, and many 
other unrelated subjects. These are followed by 
three chapters devoted to the Corollifloral and 
Apetalous Dicotyledons, and the Monocotyledons. 
There are numerous photographic illustrations. 
MANUALS OF PHYSICS. 
{1) Practical Heat, Light, and Sound. By T. 
Picton. Pp. xv+151. (London: G. Bell and 
Sons, Ltd., 1915.) Price 1s. 6d. 
(2) Notes on Practical Physics for Junior Stu- 
dents. By Prof. C. G. Barkla and Dr. G. A. 
Carse. (London: Gurney and Jackson, 1915.) 
Price @semod. net. 
(3) A Text-book of General Physics for College 
Students. By Dr. J. A. Culler. (Philadelphia 
and London: J. B. Lippincott Co., 1914.) Price 
7S. Od enete 
(4) Manuale di Fisica. Vol. ii., Acustica, Termo- 
logia, Ottica. By Prof. B. Dessau. (Milan: 
Societa Editrice Libraria, 1915.) Price 15 liras. 
(1) MALL school text-books frequently re- 
ceive but scant attention from reviewers, 
but, when it is remembered that it is exactly in 
the earliest stages of a subject that students 
should be led tp acquire those correct habits of 
thought and outlook without which real advance 
is impossible, we are not altogether persuaded that 
this attitude can be justified. It was with this in 
mind that Mr. Picton’s book for the middle forms 
of schools was examined. An experimental exer- 
cise should have for its objects, first, the eluci- 
dation of physical principles, and secondly, shou!d 
show how to conduct the measurements so as to 
obtain the best numerical result with the means at 
the disposal of the class. Most teachers will 
agree that the second of these is more easily 
secured than the first. As the preface puts it :— 
“A pupil may carry out conscientiously the written 
instructions, obtain a ‘ good result,’ write a neat 
account, and yet have very indistinct ideas (and 
often no ideas at all) of the principles under- 
lying the experiment.” To overcome this mental 
NO. 2381, VOL. 95| 

423 
inertia several questions are associated with 
each exercise, which must be answered before 
the student is allowed to proceed to the next 
experiment. The instructions are brief but suffi- 
cient, and can be thoroughly recommended for 
class-work. It may especially be noted that in 
the optical experiments a method is used which 
makes visible the paths of the rays—a consider- 
able gain at this stage. The sections on concave 
lenses need revision, as the methods given are not 
the best available; also it would be a great advan- 
tage in future work if some use were made of 
books of tables, especially of reciprocals in lens 
experiments. 
(2) Prof. Barkla and Dr. Carse’s book is appa- 
rently a collection of some of the instructions 
used in the authors’ laboratory at Edinburgh 
University. For the students there it will doubt- 
less supply all that is required in the elementary 
classes, but beyond this it is not clear that it will 
fill any gap in the existing literature. As the 
directions are not written with reference to special 
forms of apparatus, they are available for the 
senior forms of The first chapter on 
“Treatment of Observations and Determination 
schools. 
of Error” is the best elementary discussion of the 
subject that we have seen. 
(3) A comparison of English and American text- 
books of physics for colleges reveals a series of 
interesting differences. Taking them in order :— 
(1) American authors usually reduce the mathe- 
matical portions to a minimum; a rather unex- 
pected feature if it be true that instruction in the 
States is so much more systematic than here, for 
in that case the usual excuse—that the student’s 
mathematical knowledge is behind his physical 
requirements—should not be allowable. (2) More 
emphasis is placed on technical applications; a 
great advantage if the corresponding theory is 
developed. (3) There is a determination to be up 
to date as regards modern theories. 
It is this last feature that is most strikingly in 
evidence in Dr. Culler’s text-book. The author 
has set out to produce “a logical development of 
the live topics which, it seems, should be included 
in a text-book for college students,” and, on the 
logical side, has not been altogether successful. 
To give two illustrations :—He desires to explain 
all the elementary electrical phenomena in terms 
of electrons, and finds it necessary to start the 
first paragraph with ‘‘ What electricity is,” fol- 
lowed on p. 3 “Evidence for the electron 
theory,” including a description of Thomson’s 
experiments on kathode rays. Similarly, in the 
first page on magnetism we find ourselves im- 
mersed again inelectrons. In each case terms have 
to be used which, at that stage, are incapable of 
with 
